Inserting implants and replacing pivotal bone joints, particularly relatively small joints such as elbows, wrists, ankles, and knees, is a difficult process due to the relatively complex configuration of such joints. While all pivotal bone joints are defined by an intersection and cooperation of proximal and distal heads of different bones, held together by a plurality of ligaments, relatively smaller pivotal joints, such as elbows, wrists, ankles, and knees have a large number of bones, including a large number of relatively fine bones, the heads of which have many different configurations. Designing a replacement joint, a partial replacement joint, or a repair implant, against which proximal and distal heads with different configurations can articulate smoothly presents a complex task for joint repair and replacement implant manufacturers and for orthopedic surgeons.
For example, an elbow comprises a junction of three different bones, the heads of which have different configurations. An upper arm, or humerus, has a distal end, comprising a trochlea and a capitellum, defining one part of the elbow. A forearm, comprising two bones, a radius and an ulna, have proximal heads, defining another part of the elbow. The proximal head of the ulna includes, on one side a coronoid process, and on an opposite side, an extending olecranon, which cooperate to define a trochlear notch. A trochlea of the distal end of the humerus pivots in this trochlear notch. In addition, a medullary cavity is an elongated narrow cavity in the ulna storing bone marrow. The shape, surface roughness, and proper articulation of all of these bone components must be considered when designing a suitable elbow replacement or partial replacement assembly. In addition to the heads of these bones, the elbow includes soft tissue, e.g., ligaments, collagen fibers, and so forth must be accounted for when designing a suitable replacement or partial replacement assembly.
Similar issues arise when designing repair or replacement implants for pivotal joints such as wrists, ankle, and knees, which likewise are defined by cooperation of proximal and distal heads of a plurality of bones, ligaments, and other soft tissue.
For these and other reasons, it is common in the field when patients experience damage to pivotal joints, resulting, e.g., from over-work, hyper-extension, falling, or playing contact sports, to treat the pain, e.g., with pain-killers, heat and cold, and external supports, rather than by repairing or replacing the joint.
Another type of problem can occur with a shoulder joint when a patient experiences an injury to a rotator cuff. Like other joints, the shoulder is defined by cooperation of proximal and distal heads of several bones, e.g., a proximal head of a humerus, a distal head of a clavicle, a Glenoid Socket, and an A.C. socket. Soft tissue includes, among others, a group of muscles and tendons known as a rotator cuff, which stabilizes the shoulder. A natural upper surface of the humeral head is smooth, and acts as a gliding surface between the humeral head and the rotator cuff. The rotator cuff, however, is subject to damage resulting from, e.g., over-work, sudden violent movements, attempting to lift an overly-heavy weight, playing contact sports, and so forth. Motion of an injured rotator cuff across the head of the humerus can be painful. Moreover, if the rotator cuff injury is severe or not repaired promptly, a condition known as rotator cuff arthropathy may occur, i.e., formation of an arthritic rough area on the humeral head. Movement of soft tissue across this rough bone surface is even more painful.
There is a need for improved assemblies in the field of elbow repair and replacement, repair implants for other pivotal joints, and assemblies for repair of rotator cuff injuries, including but not limited to rotator cuff arthropathy.